#include <iostream>
#include <fstream>
#define MAXIM 5000001
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
int v[MAXIM],A[MAXIM];
int main()
{
    long long suma=0;
    int N,K,ok1=1,ok2=0,i;
    f>>N>>K;
    for(i=1; i<=N; i++)
        f>>A[i];
    for(i=1; i<=N; i++)
    {
        while(A[i]<A[v[ok2]] && ok1<=ok2)
            ok2--;
        v[++ok2]=i;
        if(v[ok1]==i-K)
            ok1++;
        if(i>=K)
            suma+=A[v[ok1]];
    }
    g<<suma;
    f.close();
    g.close();
    return 0;
}